Production of petroleum



Jan. 4, 1944. L DER AHE ET AL 2,338,217

PRODUCTION OF PETROLEUM Filed Dec. 14, 1940 Karl z. riii'giiie Henry Zwezfel ATTORNEYS Patented Ja n 4, 1944 2,338,217 I raonucrron or rcraornuu Karl L. Vonder Ahe, Long Beach, and Henry C.

Zweifei, Los Angeles, Calif;, assignors to Richfield Oil Corporation, Los Angeles, Calii., a corporatlon of Delaware Application December 14, 1940, Serial No. 370,180

3 Claims.

This invention relates to improvements in the drilling of wells such as those from which petroleum is produced. In one conventional method of well dril g, so-called rotary drilling, a cuttinghead carried by an advancing string of drill pipe is rotated, by rotating the drill pipe at, the head on redrilling through such a cement filled fault the hole is frequently forced out of line. Another method is to force fibrous material into the hole of the well, as it progresses with the hole while circulation of a drilling liquid downwardly through the drill pipe and upwardly through the hole around the drill pipe is maintained to carry the cuttings produced by operation of the cuttingheadout of the hole. The drilling liquids used vary widely in nature and composition. In general, the drilling liquid must be appropriate to the particular formations through which the particular well is being drilled and the composition and quality of the particular drilling liquid must be maintaind within reasonably close limits as the drilling progresses. The commonest of the drilling liquids are the so-called "drilling muds, aqueous suspensions of clay or the like, but many other drilling liquid are widely used, oil base drilling liquids for example. These drilling liquids usually comprise a variety of addends such as finely divided calcium carbonate" or pulverized barites for special purposes, such a weighting of the drilling liquid to assist in balancing gas pressures or to promote suspension of the cuttings and to render, any cake or plaster deposited from the drilling liquid susceptible of easy disintegration as with hydrochloric acid. The "specialized nature of these drilling liquids, the requirement for reasonably close control in composition and quality of the drilling liquid used in any particular operation and the relatively large volume of drilling liquid required particularly in drilling deeper holes, mak the drilling liquid and its maintenance an important element of the cost of drilling. One of the difliculties frequently encountered in such drilling operations is so-called loss of circulation, that is loss of drilling liquid from the hole. This may occur for a variety of subterranean reasons which are difficult to deal with because of their location frequently thousands of feet below the surface in the wall of a hole something less than a foot in diameter. Such loss of circulation may terminate the drilling operation until the fault can be corrected. Even though the drilling operation can be continued by the use of added quantities of drilling liquid, the loss of drilling liquid entailed is a serious cost burden. In extreme cases the hole may be lost altogether as a result of lost-circulation; Various methods of dealing with this problem havebeen used. One is to fill the hol in the region of th fault with a cement plug and then to redrill the hole through the cement plug. This is sometimes satisfactory but not generally so. Sometimes the nature of the fault would require the delivery of quantities in the region of the fault to establish an initial partial closure of the fault and then to seal of! the fault with cement or by building up a mud cake from the drilling liquid upon the inner sur face of the fibrous material forced into the fault. This method too has its limitations. For example, hundreds of bales of hay have been forced down a single hole in attempts to correct loss of circula- 'tion in this manner. This invention provides a method of correcting lost circulation in such drilling operations which has a number of advantages.

Ammoniacal solutions of casein react with formaldehyde to form a resinous condensation prodnot which ultimately becomes hard and horny. The reaction proceeds with reasonable rapidity but the reaction mixture remains liquid, in the sense that it can be forced to flow under pressure, for some little time. Casein solutions of relatively high concentration and relatively low viscosity can be produced to be supplied to the reaction, but with proper control ammoniacal casein solutions of relatively high concentration.

and relatively high viscosity can be produced. These properties of these reactants and this reaction product are applied in the practice of this invention to provide a particularly advantageous method of correcting lost circulation in Well drilling with a circulating drilling liquid.

In carrying out this invention, when loss of circulation is encountered in such a drillingv operation, an ammoniacal solution of casein is spotted at the point of circulationloss in the hole and formaldehyde is then introduced into the of cement impossible in any practical sense. Also s thus spotted casein solution and the resulting condensation product is deposited in or over the fault as a seal preventing further loss of circulation upon resumption of drilling. The rate at which the casein solution, or the reaction mixture, moves into the fault can be controlled by regulating the viscosity of the'casein solution or by permitting the reaction to continue to some intermediate point short of solidification of the condensation product before the reaction mixture is moved into the region of the fault. Also, pressure 'canbe imposed upon the reactionmixture while it is still liquid to force it into the fault. The reaction mixture may be spotted by floating it on a body of drilling liquid below the fault and raising the drilling liquid to spot the reaction mixture as required, or it may be positioned as a plug in the hole separating a body of drilling liquid in the hole below'it and another in the hole above it. In the latter case the casein solut on, or the reaction mixture, is weighted with any of the conventional weighting agents to correspond in density to that of the drilling liquid if without such weighting it I is of lower density.

The practice of the invention will be further described in connection with the accompanying drawing which illustrates, in vertical section, a portion of a hole including a fault involving loss of drilling liquid. The fault I is indicated at the left of the hole 2. Drilling liquid is indicated at 3 and l and an ammoniacal solution of casein is indicated at 5. The lower end of the string of tubing suspended from the well head is indicated at 6. Loss of circulation having developed, the string of drilling pipe and cuttinghead are withdrawn from the well. A body of an ammoniacal solution of casein is then spotted at the point of circulation loss over the body of drilling liquid 3. The ammoniacal solution-of casein is delivered at this point through the tubing 6. The ammoniacal casein solution may consist for example of a mixture of casein and ammonium hydroxide, 3 to 4 pounds of ammonium hydroxide (NH'iOH) per 100 pounds of casein, with sufiicient water to produce a solution of the required viscosity for handling, say 200-600 pounds of water per 100 pounds of casein. Formaldehyde is then introduced into the ammoniacalcasein solution,

for example by means of a dump bailer lowered.

formaldehyde and the casein solution and thus to promote the reaction. With respect to a fault such as indicated at i, for example, the ammoniacal casein solution may be spotted between lev-.

els A and B approximately, but so spotted it will be flowing into the fault as the reaction proceeds. For some types of fault this is satisfactory procedure but with others the loss of the reaction mixture is too great. The rate of flow of the reaction mixture through the fault is determined by the pressure at this point and by the viscosity initially of the ammoniacal casein solution and then of the reaction mixture. The viscosity of the ammoniacal casein solution can be varied from that of a relatively thin liquid to that of a fairly heavy slurry by limiting the proportion .of water. To facilitate delivery of the casein solution to the region of the fault or to promote penetration of the fault, the casein solution may be initially delivered as an alkaline solution consisting for example of a mixture of casein and either caustic soda or sodium carbonate, 2 /2 pounds: to 3 pounds of caustic soda or 5 to 6 pounds of sodium carbonate per 100 pounds of casein with the appropriat proportion of water and this solution may then be rendered ammoniacal, after delivery in the region of the fault, by the addition of ammonium chloride, for example about 5 to 6 pounds of ammonium chloride per 100 pounds of casein. As the reaction proceeds the through the reaction mixture into the body of ery through the tubing 6, after positioning the lower end of the string of tubing in the region of the fault, by weighting the casein solution or the reaction mixture with a weighting agent consistent with the drilling liquid so that the density of the casein solution or the reaction mix- ,ture corresponds to that of the drilling liquid. With the ammoniacal casein solution thus spotted, the inventionis carried out as previously described. A pressure can be imposed upon the reaction mixture while it is still liquid to-force it into the fault by applying pressure to the superimposed drilling liquid. The reaction mixture would in any event be under that pressure corresponding to the height of the column of superimposed drilling liquid.

With the fault sealed, the drilling operation is resumed as usual. .Reaming in or redrilling through the region of the fault may be avoided if the reaction mixture has been forced substantially completely outof the hole into the fault. However, the condensation product of the reaction does not impose any serious difiiculty upon such operations if they are necessary and has little if any tendency to force the hole out of line in connection with such operations. One of the important advantages of the invention is the extent to which it afiords control of the corrective operation in the region of the fault even though the fault is remote from the head of the well. A number of other advantages flow from this primary advantage, for example the adaptability of the invention to a variety of types of fault and to culation loss in the hole and introducing formaldehyde into the thus spotted casein solution.

2. In well drilling with a circulating drilling liquid when loss of circulation is encountered, the improvement which comprises spotting an ammoniacal solution of casein at the point of circulation loss in the hole and introducing formaldehyde into the thus spotted casein solution, and imposing pressure upon the resulting mixture while still liquid to force it into the fault.

3. In well drilling with a circulating drilling liquid when loss of circulation is encountered, the

improvement which comprises spotting an ammoniacal solution of casein weighted to-correspond in density to that of the drilling liquid at the point of circulation loss in the hole and introducing formaldehyde into the thus spotted casein solution.

KARL L. .VONDER AHE.

HENRY C. ZWEIFEL. 

